Bug 17510: update MMT-related unit tests

Bug 17510: update MMT-related unit tests

The unit tests related to MARC modification templates need to be
updated with extra tests specific to actions involving subfield 0.

Test plan:
0) Apply the patch.
1) Run the updated unit tests, they should pass without any errors:
   $ prove t/SimpleMARC.t
   $ prove t/db_dependent/MarcModificationTemplates.t

Signed-off-by: Lisette Scheer <lisettes@latahlibrary.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>